Sand Control: Sand Characterization, Failure Mechanisms, and Completion Methods

Abstract Sand production has historically been a problem associated with some consolidated, poorly consolidated, and unconsolidated sand formations. The result is usually lost production due to formation sand and fines plugging gravel packs, screens, perforations, tubular, and surface flow lines or separators. Completion methods applied to minimize sand production include: gravel packing, sand consolidation, critical production rate, oriented/selective perforation, FracPacking, or any combination of these methods. These techniques are used in consolidated, poorly consolidated, and unconsolidated sand formations. However, there are no guidelines available in the literature on how these methods are selected. Mechanisms for sand failure include: tensile, shear, cohesive, and pore collapse. Additionally, failure due to chemical effects can occur when the cementation materials are weakened due to chemical interactions. Many mathematical models have been presented in the literature to predict sand failure, and consequently determine sand production. These models are based on different failure mechanisms and include: pressure drawdown/compressive strength, failure based on a given failure criterion such as Mohr Coulomb, cohesive strength failure, elastoplastic failure around a perforation, viscoplastic modeling, and empirical correlations. However, there are no guidelines on how these models are applied based on the characteristics of the sand formation. Experimental studies have been presented in the literature to model sand failure. These studies include sand arching, hollow cylinder strength, triaxial and hydrostatic, and large scale testing. Laboratory testing are designed to study a given failure mechanism, and thus to predict sand production. The objective of this paper is to categorize sand formations that potentially exhibit sand failure and sand production. Based on this characterization, an appropriate laboratory testing and mathematical modeling are recommended, and a completion method is suggested. Examples from standstone reservoirs in Saudi Arabia will be used to demonstrate certain methods used for sand control.